Harmonic diagnosing method for electric facility

ABSTRACT

The present invention relates to a method of diagnosing deterioration by comparing an index value which is obtained by dividing the relative harmonic content of each order of the current harmonics flowing into an electric motor and inverter by the total harmonic distortion of the current harmonics up to the predetermined order, with a criteria value which is obtained by multiplying a harmonic function of each order formed of the index value by a calculated value for diagnosis of each order found through calculation from the relative harmonic content of each order. In the method, the degrees of deterioration of the electric motor and inverter are distinguished from each other by weighting the criteria value, and the deteriorated part is determined by a specific harmonic order of the current harmonics.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Application No.PCT/JP2004/001154, filed Feb. 4, 2004, entitled HARMONIC DIAGNOSINGMETHOD FOR ELECTRIC FACILITY, which claims priority to Japanese PatentApplication No. 2003-36362, filed Feb. 14, 2003, entitled METHOD OFHARMONIC DIAGNOSIS FOR ELECTRIC EQUIPMENT, which claims priority toJapanese Patent Application No. 2003-30807, filed on Feb. 7, 2003,entitled METHOD OF HARMONIC DIAGNOSIS FOR ELECTRIC EQUIPMENT, all of theabove disclosures are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention belongs to the technical field of electricequipment diagnosis, and relates to a method of harmonic diagnosis forelectric equipment such as motors and inverters.

2. Description of the Related Art

Recent electric equipment has been tried to improve its productivity bya continuous and integrated production process. Furthermore, an energysaving device such as an inverter has been introduced together with ahigh-performing automated system in a wide range so as to achieve highlyreliable equipment. Such mass production is being required in everyindustrial field.

Mass production equipment is generally operated continuously, and abreakdown (stoppage) in electric equipment often brings the entireprocess into a standstill. Once there is a breakdown, it not onlydamages production process but also loses the reliability of users, andmay even cause a disaster. Thus, the downtime loss is immeasurable, andmay lead to a fatal problem.

When they purchase brand new equipment (machine) and check it,enterprises perform the checking by making sure that the equipment(machine) operates according to its specification because at presentthere is no checking standards or unified rules. However, since recentautomatic devices (machinery) have a combined system structure in whicha lot of devices are connected via interface cables, there might be nomatching between these systems, thus causing a lot of troubles later, oreven fire accidents.

Furthermore, transportation equipment such as railroad trains andelevators to carry people are obliged to have a periodic inspection bystatute; however, power conversion equipment (AC-AC converter) includingmotor equipment and inverters are checked only for the presence orabsence of a temperature rise or abnormal noise, leaving safety problemsunsolved.

The objects of diagnosing abnormalities and deterioration of theelectric equipment include: to improve operation rate by reducing thedowntime of the equipment; to reduce maintenance costs includingmaterial and labor costs; to reduce other costs by extending thereplacement period and reducing the inspection maintenance; to preventtroubles; and to improve safety, reliability, productivity and quality.

Described above are the background and objects of the necessity ofdiagnosing abnormalities and deterioration of electric equipment. Theconventional way of diagnosing abnormalities and deterioration inelectric motors and inverters according to the present invention will bedescribed in brief in the following sections 1 and 2.

1. Diagnosis of Abnormalities and Deterioration for Electric Motors

Methods of diagnosing abnormalities and deterioration for electricmotors include: (1) vibration methods; (2) acoustic methods; (3)temperature methods; (4) torque methods; (5) current methods; and (6)waveform methods. Of these methods, vibration methods, which are themost frequently used methods, will be described as follows. The otherdiagnosing methods are omitted patents filed by the inventor of thepresent invention (Japanese Patent Applications No. 2000-386603, No.2001-265949, No. 2001-358718, and No. 2003-030807).

Vibration methods have a simple diagnosis and a precise diagnosis. Inthe simple diagnosis, an abnormality is determined by a vibrationoverall value of a rotary machine in an electric motor or load equipmentincluding an electric motor by installing a vibration pickup ofelectrokinetic type, piezoelectric type or displacement type as close tothe source of vibration as possible. In the precise diagnosis, the causeand location of an abnormality and deterioration are determined by thefrequency analysis of vibration. These diagnoses are both restricted tomechanical elements such as bearings and rotary shafts.

As described above, for the simple diagnosis, some enterprises havetheir own standards to determine between abnormality and normality by avibration overall value based on the accumulated data and experience.However, most other enterprises depend on the ISO standard, the JISstandard or the VDI standard (the standard of the association of GermanEngineers). These standards, however, provide only average evaluations,and cannot be applied to all rotary machines. For example, the ISOstandard and the JIS standard have ISO-2372 and JIS-B0906, respectively.

When an abnormality is determined by the simple diagnosis, a precisediagnosis is required to determine the cause and location. In general,vibration signals generated from rotary machines are complicated, andare hardly simple. In order to obtain significant information from thesignals to precisely determine the presence or absence of anabnormality, frequency analyses are most widely used. Applying afrequency analysis to a vibration signal makes it possible to determinethe cause and location of the abnormality.

For the rotary machines including these electric motors, the relationbetween the cause of an abnormality and the number of vibration eventsis not accurate because it is obtained from the data accumulated over along period.

2. Diagnosis of Abnormalities and Deterioration for Inverters

Inverters have the advantages of saving energy, and improvingproductivity and operability so as to contribute to the achievement ofhigh-tech industrial machines of various kinds. Inverters are nowessential devices in motor equipment, and their production amount isincreasing year by year. The production amount of industrial invertersin Japan in the fiscal year of 1999 exceeded 1,800,000 (equivalent toabout 100 billion yen) according to MITI (present METI) Current Surveyof Production.

By the way, an inverter is formed of a lot of parts including electronicparts such as ICs, resistors, capacitors and transistors, and otherparts such as cooling fans and relays. These components cannot be usedpermanently, and their durable years greatly depend on the operatingenvironment. Almost all the electronic parts have operating lives incompliance with Arrhenius law (the rule of doubling for every 10° C.:operating life doubles for every 10° C. reduction in the ambienttemperature), so the inverter needs a periodic inspection.

As a diagnosis of abnormalities and deterioration for inverters, theJEMA (Japan Electrical Manufacturers' Association) recommends a periodicinspection in their guidebook “An encouragement of Periodic Inspectionof General-Purpose Inverter” to prevent potential troubles.

However, in a diagnosis of abnormalities and deterioration for aninverter, the determination of the cause and location of an abnormalityand deterioration requires the inverter to be stopped or even decomposedso as to be checked by a specialist with a special measuring device. Inreality, inverters are often used until they are down. During theperiods, the inverters often cause deterioration in their functions suchas energy saving function and protection function, and also causeabnormalities in their output properties. In addition, the invertersoften adversely affect other devices, such as causing robot malfunctionor electric motor trouble.

SUMMARY OF THE INVENTION

Of diagnoses of abnormalities and deterioration for electric motors andinverters, the vibration methods are most widely used for electricmotors. Since its installation affects the precision of an electricmotor, the pickup must be fixed near the source of vibration. Inaddition, the location of an abnormality and deterioration to bediagnosed is restricted to mechanical elements such as bearings androtary shafts. Furthermore, the measurement takes time, and thediagnosis cost including the measuring device is expensive. For thesereasons, this diagnosis method is used mainly for comparativelylarge-sized machines with high importance.

The description of the other diagnosis methods for electric motors isomitted. Unlike vibration methods, all these methods cannot determinethe cause and location of an abnormality and deterioration, and aboveall, online survey systems, which can diagnose abnormal load only, areextremely expensive.

In addition, in a diagnosis of abnormalities and deterioration for aninverter, as described earlier, the determination of the cause andlocation of an abnormality and deterioration requires the inverter to bestopped or even decomposed so as to be checked by a specialist with aspecial measuring device. This is extremely troublesome, time consuming,and costly.

In order to diagnose deterioration for electric motors and inverters,the inventor of the present invention filed Japanese Patent ApplicationsNo. 2000-386603, No. 2001-265949 and No. 2001-358718 as new methods ofdetermining the degrees of deterioration of electric motors andinverters and its cause and location by the size of a relative harmoniccontent in the current.

However, these harmonic diagnosis methods by the inventors of thepresent invention are absolute methods in which calculation is performedby previously acquiring the rated capacities, power source impedance,and load factor of electric motors and inverters, the parallelequivalent capacity of the load of other than these devices, the servicevoltage, the types of harmonic measures and the like. These are notnecessarily simple methods, taking time for diagnosis. Furthermore, therelation between harmonics and the location of deterioration, that is,the deteriorated part is not clear.

The method of harmonic diagnosis for electric equipment such as electricmotors and inverters according to the present invention can solveproblems owned by the inventors' harmonic diagnosis that is based on theaforementioned absolute methods as follows.

In a method of diagnosing deterioration to determine an abnormality ofan electric motor or an inverter from current harmonics which flow intothe electric motor and inverter that form the electric equipment,deterioration is determined by comparing an index value which isobtained by dividing the relative harmonic content of each order of thecurrent harmonics by the total harmonic distortion of the currentharmonics up to the predetermined order, with a criteria value which isobtained by multiplying the harmonic function of each order formed ofthe index value by a calculated value for diagnosis of each order foundthrough calculation from the relative harmonic content of each order.The degrees of deterioration of the electric motor and inverter aredistinguished from each other by weighting the criteria value, and thedeteriorated part is determined by a specific harmonic order of thecurrent harmonics.

The harmonic diagnosis method for electric equipment according to thepresent invention is performed by measuring the current harmonicsflowing into the electric motor and inverter, however, this method doesnot depend on the capacities of the electric motor or inverter. Thismethod is also irrespective of power source impedance, load factor, theparallel equivalent capacity of the load of other than these devices,the service voltage, the types of harmonic measures and the like,thereby being an extremely simple diagnosis method.

Furthermore, the relation between the harmonics and the deterioratedpart of the electric motor and inverter has been clarified by using abasis analytical method. Since it becomes possible to distinguishbetween the degrees of deterioration based on the basis analyticalmethod, the method of harmonic diagnosis according to the presentinvention is extremely practical, with the potential of spreading to theindustrial society.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an inverter.

FIG. 2 is a view to explain the generation of harmonics.

FIGS. 3A to 3H are examples of oscillating current waveforms, andautocorrelation functions corresponding to them,

FIG. 4 is a flowchart to diagnose the electric motor.

FIGS. 5A to 5C are flowcharts to diagnose the inverter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment of the present invention will be described as followswith reference to drawings.

FIG. 1 is a block diagram of an inverter. The reference numeral 1represents a three-phase AC power source, and input power 1′ is flown toa converter part 4 of an AC-AC converter 3 which controls an electricmotor 2. The reference numerals 5 and 6 represent a smoothing capacitorand an inverter part, respectively, and output power 2′ is controlled bya control part 7 and a drive part 8. The control part 7 and the drivepart 8 are a control board and a drive board, respectively, havingelectronic parts such as ICs, resistors, capacitors and transistorsmounted on them. When the AC-AC converter 3 is based on a sinusoidalwave PWM technique, the input current and the electric motor current(output current) have the waveforms shown in FIG. 1.

The AC-AC converter 3 has the input current shown in FIG. 1 because ofthe presence of the smoothing capacitor 5 after the converter part 4rectifies all the waves. This phenomenon will be described as follows.

FIG. 2 shows examples of the generation of single-phase harmonics. Sincethe smoothing capacitor 5 shown in FIG. 1 is used to convert athree-phase AC power source into a DC power source, a pulse-like currentas shown in FIG. 2 is flown to the capacitor 5 only during the charge.In the drawing, c represents a pulse width and H represents its height.The difference in flow between the AC power source and the DC powersource generates harmonics.

By the way, when a sinusoidal current is supplied to the U phase, Vphase and W phase of the electric motor, the magnetomotive forces F_(u),F_(v) and F_(w) are respectively expressed by the following equations.F _(u) =AI _(u) sin ωt[cos θ−(⅓)cid3θ+(⅕)cos 5θ+. . . ]F _(v)=AI_(v) sin(ωt−120°)[cos(θ−120°)−(⅓)cos 3(θ−120°)+(⅕)cos5(θ−120°)+. . . ]F _(w)=AI_(w) sin(ωt−240°)[cos(θ−240°)−(⅓)cos 3(θ−240°)+(⅕)cos5(θ−240°)+. . . ]  (Numerical Formula 1)

The numerical formula 1 indicates a magnetomotive force at a distance ofθ (electrical angle) on the circumference using the center of themagnetomotive force of the rotor as the base point. A represents aconstant; I_(u), I_(v) and I_(w) represent the effective values of thecurrents at the U phase, V phase and W phase, respectively; ω is anangular velocity expressed by 2nf (rad/s) when the frequency is f, and trepresents time. Consequently, the synthesized magnetomotive force F inthe case of taking the nth-order harmonics into consideration is asfollows.F=(3B/2) F_(m)(sin(θ−ωt)+(K _(1,5)/5)sin(5θ+ωt)+(K_(1,7)/7)sin(7θ−ωt)+(K_(1,11)/11) sin(11θ+ωt)+(K_(1,13)/13)sin(13θ−ωt)+. . . )  (Numerical formula 2)

where B represents a constant, F_(m) represents the maximum value of theamplitude of the magnetomotive force of the fundamental wave, andK_(1,n) represents a winding factor of the nth order harmonics.

The numerical formula 2 indicates the following.

(1) When I_(u)=I_(v)=I_(w) harmonics such as n=3, 9, 15, . . . becomezero.

(2) The harmonics such as n=5, 11, 17, . . . rotate at ω/n in thedirection opposite to the fundamental wave.

(3) The harmonics such as n=7, 13, 19, . . . rotate at ω/n in the samedirection as the fundamental wave.

On the other hand, let the current waveform shown in FIG. 2 be a squarepulse wave, f(x) can be expressed by Fourier series in the followingnumerical formula.

(Numerical Formula 3)

${f(x)} = {\sum\limits_{n = 1}^{\infty}{\left( {{H/n}\;\pi} \right)\left( {1 - {\cos\; n\;\tau}} \right)\sin\; n\; x}}$

where x=ωt(ω: angular velocity, t: time) and n represents the order ofthe harmonics. As apparent from the numerical formula 3, when thesmoothing capacitor 5 is ideal, there is no flow of a pulse-like currentresulting from a charge current, so that f(x)=0. With the deteriorationof the smoothing capacitor 5, the capacitance decreases, and harmoniccomponents having low orders such as n=5, 7 increase in the numericalformula 3. Note that n=3, or the 3rd harmonics are extremely small as isunderstood from the numerical formula 1 (zero in the case ofI_(u)=I_(v)=I_(w)).

The relation between the current harmonics and the state ofdeterioration of the electric motor and inverter has been firstclarified by the inventors of the present invention. The contents are asfollows.

The electric motor is designed to contain as little harmonics aspossible because it contains harmonic components in the magnetomotiveforce as shown in the numerical formula 2. Even so, the unbalance ofpower supply voltage and the like causes harmonics larger than atheoretical value. In addition, the inverter also generates harmonics asis well known.

The deteriorated part of the electric motor will be described asfollows. The deteriorated part can be either a mechanical element suchas a bearing and a rotary shaft or an electric element such as a statorwinding. Particularly, when deterioration occurs in the mechanicalelement, the electric motor current contains an irregular vibrationalcomponent. It goes without saying that this includes regular harmoniccomponents. Consequently, only the essential harmonic parts can be takenout from the random irregular current waveform by taking anautocorrelation function R (τ) shown in the following numerical formula.

(Numerical Formula 4)

${R(\tau)} = {\lim\limits_{T->\infty}{\frac{l}{T}{\int_{{- T}/2}^{T/2}{{{f(t)} \cdot {f\left( {t + \tau} \right)}}{\mathbb{d}t}}}}}$

where t: time, τ: 1/f₀(f₀ rotation frequency), T: time.

FIGS. 3A, 3B, 3C and 3D are examples of random current waveforms fromwhich the fundamental wave components have been removed, and theautocorrelation functions corresponding to them are shown in FIGS. 3E,3F, 3G and 3H, respectively. FIGS. 3A-3H indicate that when it is foundthat f changes at random every second by taking the autocorrelationfunction, R takes on a value only when τ=0, and becomes 0 in the othercases. Therefore, in case of the waveforms shown in FIGS. 3A, 3B, 3C and3D, FIG. 3D has the highest correlation between the harmonics.

When deterioration occurs in an electric element such as a statorwinding, changes in the magnetic flux inside the coil conductor causesan eddy current flowing like an eddy only inside the conductor. Thiseddy current induces local heating in the deteriorated part of a coilinsulator, thereby causing unbalance between the respective phasecurrents. This results in I_(u)≠I_(v)≠I_(w) in the numerical formula 1,with conspicuous 3rd-order harmonics. Furthermore, the 3rd-orderharmonics repeat the phenomenon of further increasing the local heatingin the deteriorated part.

On the other hand, about the deterioration of the inverter, thesmoothing capacitor 5 shown in FIG. 1 has been described above. When theother electric elements (the converter part 4 and the inverter part 6),the control part 7, and the drive part 8 are deteriorated, the harmoniccomponents increases in the current of the output power 2′ shown in FIG.1, thus exhibiting an extraordinary value. The inventors have found thatthe deterioration of the inverter and the deterioration of the electricmotor are related to a plurality of specific harmonics. The following isa description about determination of such deterioration.

FIG. 4 is a flowchart to diagnose the electric motor. Step S10 finds thetotal harmonic distortion (THD) of the harmonics contained in thecurrent of the output power 2′ shown in FIG. 1. The detection of thecurrent harmonics can be done by using a well-known device such as aclamping measure or a non-contact electromagnetic field measure with asearch coil. The harmonic orders from which to find the total harmonicdistortion can be, for example, the 2nd to 40th orders. Step S11performs index calculation to find an index value (TH_(k)) obtained bydividing the relative harmonic content of each order by the totalharmonic distortion found at Step S10.

Then, the process goes to step S12 to determine deterioration. CH_(k) isa criteria value of the Kth-order harmonics which will be describedlater, and is compared with TH_(k) found at Step S11. As a result, theprocess goes to Step S13 when the electric motor is in the normalcondition, and to step S14 when it is deteriorated. The flowchart todiagnose the inverter is shown in FIGS. 5A to 5C. FIG. 5A is a flowchartto diagnose the smoothing capacitor 5 shown in FIG. 1, and determinesdeterioration by measuring the current harmonics of the input power 1′shown in FIG. 1. Steps P100, P111 and P112 have the same calculationcontents as in the Steps S10, S11, and 512 shown in FIG. 4.

FIG. 5B is a flowchart to diagnose the converter part 4, the inverterpart 6 and the control part 7 shown in FIG. 1, and determinesdeterioration by measuring the current harmonics of the output power 2′shown in FIG. 1. Steps P200, P211 and P212 have the same calculationcontents as in the Steps P100, P111, and P112 shown in FIG. 5A.

FIG. 5C is a flowchart to diagnose the drive part 8 shown in FIG. 1, anddetermines deterioration by measuring the current harmonics of theoutput power 2′ shown in FIG. 1. At Step P200′, the 38th-order harmoniccontent is found, and the drive board is diagnosed (Step P201′). Thediagnosis of the drive board is based on the criteria value CH_(k)=1.0of the 38th-order harmonics (Step P202′). At Step P203′, CH_(k) iscompared with the 38th-order harmonic content (H₃₈) to determine thegood or bad of the drive board.

The criteria values CH_(k) shown in FIG. 4 and FIGS. 5A, 5B and 5C arefound as follows. K represents the Kth-order harmonics, and C_(k)represents a calculated value for diagnosis of the Kth-order harmonics.

Concerning the electric motor:CH _(k) =C _(k) ×f(M _(k))  (Numerical formula 5)

where f(M_(k)) is the Kth-order harmonic function.

Concerning the inverter:CH _(k) =C _(k) ×f(N _(s))CH _(k) =C _(k) ×f(N _(c))CH _(k) =C _(k) ×f(N _(p))CH _(k) =C _(k) ×f(N _(d))  (Numerical formula 6)

where f(N_(s)), f(N_(c)) and f(N_(p)) are plurality of Kth-orderharmonic functions, and f(N_(d))=1.0 (CH_(k)=1.0 in this case only).

In the numerical formulas 5 and 6, C_(k), f(M_(k)), f(N_(s)), f(N_(c))and f(N_(p)) will be explained later in the embodiment.

The degrees of deterioration of the electric motor and inverter(hereinafter referred to as devices) are discriminated into: “normal”;“caution needed”; and “defective” in order to show the quality. These“normal”, “caution needed”, and “defective” are referred to as A, B andC, respectively for convenience. The level B “caution needed” is furtherdiscriminated into: light deterioration B1 (deterioration which willcause no problem in the operation for about a half year); intermediatedeterioration B2 (deterioration which will allow about three monthoperation, but requires tendency control); and heavy deterioration B3(deterioration which requires preparation for replacement or repairbecause of the high probability of defects in the devices) depending onthe degree of deterioration of the devices.

Since the diagnosis and inspection period after deterioration depend onthe environmental conditions such as the number of the operating hoursof the devices, ambient temperature and ventilating condition, theaforementioned inspection period can be considered just as a guideline.

The aforementioned levels: A, B1, B2, B3 and C are distinguished fromeach other by multiplying a weighting factor by the aforementionedcriteria value. This factor will be described later in the embodiment. Amultivariate analysis technique is effective to perform an analysis byfocusing on the relation between the current harmonics and thedeteriorated part of the devices, so this technique will be described asfollows. In order to analyze the relation between the characteristicvalues of multidimensional events in a case where there is no externalcriteria for determination previously given as in the diagnosis ofdeterioration for devices according to the present invention, the basisanalytical method which is one of the multivariate analyses is the mostsuitable.

Since there are a lot of documents about the basis analytical method,the detailed description will be omitted. The following is a descriptionabout the relation between the current harmonics and the deterioratedpart of each of the electric motor and the inverter by using thecontribution rate of the basis analytical method. In the followingdescription, the numbers inside the parentheses following the principalcomponents indicate contribution rates. The principal components areshown in decreasing order of characteristic values (the distribution ofprincipal component scores).

1. Electric Motor

(1) Abnormalities of the rotary shaft and bearing (electric motor's mainbody) or defective installation of the electric motor. The fourprincipal components found are: the 2nd-order harmonics (55), the3rd-order harmonics (9), the 4th-order harmonics (16) and the 5th-orderharmonics (6). The cumulative contribution rate of the employedprincipal components is 86%, thereby fully satisfying 60% or more of thevalues generally employed.

(2) Poor insulation of the stator winding (between phases and to theground). The four principal components found are: the 2nd-orderharmonics (7), the 3rd-order harmonics (61), the 4th-order harmonics (5)and the 5th-order harmonics (22). The cumulative contribution rate is95%.

(3) Damages of the rolling bearing and housing (electric motor's mainbody). The four principal components found are: the 2nd-order harmonics(23), the 3rd-order harmonics (10), the 4th-order harmonics (41) and the5th-order harmonics (8). The cumulative contribution rate is 82%.

(4) Unevenness of air gaps between the stator and the rotor (dirtadhesion and local overheat). The four principal components found are:the 2nd-order harmonics (6), the 3rd-order harmonics (20), the 4th-orderharmonics (8) and the 5th-order harmonics (59). The cumulativecontribution rate is 93%.

(5) Unbalance of the load-side rotary shaft or defective coupling withthe load. The five principal components found are: the 6th-orderharmonics (5), the 7th-order harmonics (53), the 8th-order harmonics(7), the 9th-order harmonics (11) and the 10th-order harmonics (15). Thecumulative contribution rate is 91%.

(6) Damages of the load-side bearing or dirt adhesion to the load-sidesystem (for example, a piping valve of the pump). The five principalcomponents found are: the 6th-order harmonics (7), the 7th-orderharmonics (29), the 8th-order harmonics (35), the 9th-order harmonics(13) and the 10th-order harmonics (11). The cumulative contribution rateis 95%.

(7) Abnormalities of the load-side rotary shaft (for example, bending ofthe shaft) or wornout of the load-side system (for example, the couplingbetween the piping of the pump and the valve). The five principalcomponents found are: the 6th-order harmonics (5), the 7th-orderharmonics (21), the 8th-order harmonics (25), the 9th-order harmonics(33) and the 10th-order harmonics (8). The cumulative contribution rateis 92%.

(8) Damages of the load-side wheel, clutch, V-belt or the like. The fiveprincipal components found are: the 6th-order harmonics (6), the7th-order harmonics (23), the 8th-order harmonics (17), the 9th-orderharmonics (15) and the 10th-order harmonics (30). The cumulativecontribution rate is 93%.

2. Inverter

(1) Deterioration of the smoothing capacitor

The current harmonics on the inverter input side are measured, and twoprincipal components are found. The components found are the 5th-orderharmonics (62) and the 7th-order harmonics (36), and the cumulativecontribution rate is 98%.

(2) Abnormalities of the control board (in particular, deterioration ofthe electrolytic capacitor). The current harmonics on the inverteroutput side are measured, and six principal components are found. Thecomponents found are: the 11th-order harmonics (21), the 13th-orderharmonics (17), the 17th-order harmonics (19), the 19th-order harmonics(13), the 23rd-order harmonics (11), and the 25th-order harmonics (15).The cumulative contribution rate is 96%.

(3) Deterioration of electric power elements (in particular,deterioration of an inverse transformation element).

The current harmonics on the inverter output side are measured, andsixteen principal components are found. The components found are: the2nd-order harmonics (3), the 3rd-order harmonics (16), the 4th-orderharmonics (2), the 5th-order harmonics (13), the 6th-order harmonics(2), the 7th-order harmonics (17), the 8th-order harmonics (2), the9th-order harmonics (2), the 10th-order harmonics (2), the 11th-orderharmonics (6), the 13th-order harmonics (4), the 17th-order harmonics(7), the 19th-order harmonics (5), the 23rd-order harmonics (5), the25th-order harmonics (6), and the 38th-order harmonics (7). Thecumulative contribution rate is 99%.

(4) Deterioration of the drive board (mainly deterioration of thecapacitor). The current harmonics on the inverter output side aremeasured. Only one principal component is enough, and the foundcomponent is the 38th-order harmonics. The contribution rate is 89%.

In the aforementioned electric motor, in the case that it is operatedwithout being controlled by the inverter, the current harmonics on itsinput side is measured, whereas in the case that it is controlled by theinverter, the current harmonics on its output side (the motor's input)is measured.

The description hereinbefore can be summarized in Tables 1 and 2 shownbelow.

TABLE 1 Electric motor equipment's deteriorated part and currentharmonics Current harmonics Selected principle Electric First principlecomponents motor component Order (in Electric equipment's Contri-decreasing Cumulative motor deteriorated bution order of contributionequipment part Order rate (%) score) rate (%) Motor's Rotary shaft 2 552, 4, 3, 6 86 main body and bearing, installation Insulation 3 61 3, 5,2, 4 95 of stator winding (between phases or to the ground) Damage of 441 4, 2, 3, 5 82 bearing and housing Uneven air 5 59 5, 3, 4, 2 93 gaps(dirt adhesion, local overheat) Motor load Unbalance of 7 53 7, 10, 9,8, 6 91 rotary shaft, coupling Damage of 8 35 8, 7, 9, 10, 6 95 bearing,foreign matter adhesion Wornout of 9 33 9, 8, 7, 10, 6 92 rotary shaftand coupling part Damage of 10 30 10, 7, 8, 9, 6 93 wheel and beltsystem

TABLE 2 Inverter equipment's deteriorated part and current harmonicsCurrent harmonics Selected principle First principle components Invertercomponent Order (in equipment's Contri- decreasing Cumulativedeteriorated bution order of contribution Equipment part Order rate (%)score) rate (%) Inverter Smoothing  5 62 5, 7 98 capacitor Control 11 2111, 17, 13, 25, 96 board 19, 23 Electric  7 17 7, 3, 5, 17, 99 power 38,11, 25, 19, element 23, 13, 2, 4, 6, 8, 9, 10 Drive board 38 89 38 89

Note that the smoothing capacitor has harmonics on the inverter inputside, and the others have harmonics on the inverter output side.

Embodiment

As the embodiment of the present invention, the calculated value fordiagnosis and the Kth-order harmonic function which are necessary forthe deterioration determination of the electric motor and inverter willbe described as follows by taking up specific examples. However, thepresent invention is not limited to this embodiment. In the followingdescription, H_(k) is the Kth-order harmonic content.

(1) Diagnosis of the electric motor (diagnosis of the electric motor'smain body). When K=2, 3, 4 or 5, Σ takes K=2 to 5. The procedure to findC_(k) is as follows.M _(o)=(ΣH ² _(k))^(1/2)  1A _(k) =H _(k) /M _(o)  2T_(o)ΣA_(k)  3C _(k) =A _(k) /T _(o)  4

On the other hand, f(M_(k)) can be the following values. In thefollowing numerical formulas, I_(k) represents the index value of thekth-order harmonics.f(M ₂)=S ₁×(ΣI _(k) −I ³ ₂)f(M ₃)=S ₂×(ΣI _(k) −I ³ ₃)f(M ₄)=S ₁×(ΣI _(k) −I ₄)f(M ₅)=S ₂×(ΣI _(k) −I ³ ₅)

In the case of the inverter-driven motor, S₁=S₂=1.0, and in the case ofthe electric motor alone (no inverter), S₁=1.15 and S₂=1.25.

(2) Diagnosis of the electric motor (diagnosis of the electric motorload). When K=6, 7, 8, 9, or 10, Σ takes K=6 to 10. The procedure tofind C_(k) is as follows.M _(o)=(ΣH² _(k))^(1/2)  1A _(k) =H _(k) /M _(o)  2T_(o)=ΣA_(k)  3C _(k) =A _(k) /T _(o)  4

On the other hand, f(M_(k)) can be the following values. In thefollowing numerical formulas, I_(k) represents the index value of thekth-order harmonics.f(M ₇)=S ₂×(ΣI _(k) −I ³ ₇)f(M ₈)=S ₁×(ΣI _(k) −I ₈)f(M ₉)=S ₁×(ΣI _(k) −I ₉)f(M ₁₀)=S ₁×(ΣI _(k) =I ₁₀)

In the case of the inverter-driven motor, S₁=S₂=1.0, and in the case ofthe electric motor alone (no inverter), S₁=1.15 and S₂=1.25.

(3.) Diagnosis of the inverter

3.1. Diagnosis of the smoothing capacitor. When K=5 or 7, Σ takes K=5 to7. The procedure to find C_(k) is as follows.M _(o)=(ΣH² _(k))^(1/2)  1A _(k) =H _(k) /M _(o)  2T_(o)=ΣA_(k)  3C _(k) =A _(k) /T _(o)  4

On the other hand, f(N_(s)) can be the following values. In thefollowing numerical formula, I_(k) represents the index value of thekth-order harmonics.f(N_(s))=ΣI_(k)

3.2 Diagnosis of the control board. When K=11, 13, 17, 19, 23, or 25, Σtakes 11 to 25. The procedure to find C_(k) is as follows.M _(o)=(ΣH² _(k))^(1/2)  1A _(k) =H _(k) /M _(o)  2T_(o)=ΣA_(k)  3C _(k) =A _(k) /T _(o)  4

On the other hand, f(N_(c)) can be the following values. In thefollowing numerical formula, I_(k) represents the index value of thekth-order harmonics.

f(N_(c))=ΣI_(k)−I² _(k): six function values of f(N_(c))₁₁, f(N_(c))₁₃,f(N_(c))₁₇, f(N_(c))₁₉, f(N_(c))₂₃, and f(N_(c))₂₅.

3.3. Diagnosis of the electric power elements. When K=2, 3, 4, 5, 6, 7,8, 9, 10, 11, 13, 17, 19, 23, 25 or 38, Σ takes 2 to 38. The procedureto find C_(k) is as follows.M _(o)=(ΣH² _(k))^(1/2)  1A _(k) =H _(k) /M _(o)  2T_(o)=ΣA_(k)  3C _(k) =A _(k) /T _(o)  4

On the other hand, f(N_(p)) can be the following values. In thefollowing numerical formula, I_(k) represents the index value of thekth-order harmonics.

f(N_(p))=ΣI_(k)−I² _(k): sixteen function values of f(N_(p))₂,f(N_(p))₃, f(N_(p))₄, f(N_(p))₅, f(N_(p))₆, f(N_(p))₇, f(N_(p))₈,f(N_(p))₉, f(N_(p))₁₀, f(N_(p))₁₁, f(N_(p))₁₃, f(N_(p))₁₇, f(N_(p))₁₉,f(N_(p))₂₃, f(N_(p))₂₅, and f(N_(p))₃₈.

3.4. Diagnosis of the drive board. As mentioned earlier, the drive boardis diagnosed only by the size of the 38th-order harmonic content asshown in FIG. 5C. Therefore, C_(k)=1.0, and f(N_(d))=1.0.

Examples of the electric equipment's deteriorated part and thedistinction between the degrees of deterioration (A, B1, B2, B3 and C)described in the embodiment of the present invention are shown in Tables3 and 4 below.

TABLE 3 The electric motor's deteriorated part and the distinctionbetween the degrees of deterioration Electric Electric motor MotorEquipment's Normal Caution needed (B) Defective equipment deterioratedpart (A) (B) (B2) (B3) (C) Electric Rotary shaft and C₂ × f (M₂) (A) ×(B1) × (B2) × (B3) or motor's bearing, 1.3 1.3 1.2 more main bodyinstallment Insulation of C₃ × f (M₃) (A) × (B1) × (B2) × (B3) or statorwinding 1.3 1.3 1.2 more (between phases or to the ground) Damage ofbearing C₄ × f (M₄) (A) × (B1) × (B2) × (B3) or and housing 1.3 1.3 1.2more Uneven air gaps C₅ × f (M₅) (A) × (B1) × (B2) × (B3) or (dirtadhesion, 1.3 1.3 1.2 more local overheat) Motor Unbalance of C₇ × f(M₇) (A) × (B1) × (B2) × (B3) or load rotary shaft, 1.2 1.2 1.1 morecoupling Damage of bearing, C₈ × f (M₈) (A) × (B1) × (B2) × (B3) orforeign matter 1.2 1.2 1.1 more adhesion Wornout of rotary C₉ × f (M₉)(A) × (B1) × (B2) × (B3) or shaft and coupling 1.2 1.2 1.1 more partDamage of wheel C₁₀ × f (M₁₀) (A) × (B1) × (B2) × (B3) or and beltsystem 1.2 1.2 1.1 more

where C_(k): the calculated value for diagnosis of the Kth-orderharmonics, f(M_(k)): Kth-order harmonic function

TABLE 4 The inverter equipment's deteriorated part and the distinctionbetween the degrees of deterioration The inverter equipment'sdeteriorated Normal Caution needed (B) Defective Equipment part (A) (B1)(B2) (B3) (C) Inverter Smoothing C_(K) × f (N_(s)) (A) × 1.1 (B1) × 1.1(B2) × 1.1 (B3) or capacitor more Control C_(K) × f (N_(c)) (A) × 1.3(B1) × 1.3 (B2) × 1.2 (B3) or board more Electric C_(K) × f (N_(p)) (A)× 1.3 (B2) × 1.3 (B2) × 1.2 (B3) or power more element Drive board C_(K)× f (N_(d)) (A) × 1.3 (B1) × 1.3 (B2) × 1.2 (B3) or more

where C_(k): the calculated value for diagnosis of the kth-orderharmonics, f(N_(s), N_(c), N_(p), N_(d)): kth-order harmonic functions.

Note that the numbers in C_(k) and f(N_(s), N_(c), N_(p), N_(d)) shownin Table 4 correspond to two smoothing capacitors, 6 control boards, 16electric power elements, and one drive board. Consequently, for thedistinction between the degrees of deterioration, the degrees ofdeterioration are found separately excluding the drive board and areaveraged. For example, calculation is done with A=0, B1=1, B2=2, B3=3,and C=4 and average is taken (round off the decimals).

As described hereinbefore, measuring current harmonics can determine thedeteriorated part of an electric motor or inverter of electricequipment, and also can distinguish between the degrees ofdeterioration.

1. A method of harmonic diagnosis for electric equipment to determine anabnormality of an electric motor or inverter from a current harmonicflowing to said electric motor and inverter that form electricequipment, comprising: comparing an index value, which is obtained bydividing a relative harmonic content of each order of current harmonicsby total harmonic distortion of the current harmonics up to apredetermined order, with a criteria value, which is obtained bymultiplying a harmonic function of each order found through calculationfrom the relative harmonic content of each order, wherein the degrees ofdeterioration of said electric motor and inverter are distinguished fromeach other by weighting said criteria value, and a deteriorated part isdetermined from a specific harmonic order of said current harmonics,used to prevent abnormality of the electric motor or inverter.
 2. Themethod of harmonic diagnosis for electric equipment according to claim1, wherein the specific harmonic orders are at least one odd order andat least one even order.
 3. The method of harmonic diagnosis forelectric equipment according to claim 2, wherein the at least one oddorder includes odd orders and the at least one even order includes evenorders and the odd orders and the even orders are the 2^(nd) order, the3^(rd) order, the 4^(th) order, the 5^(th) order, the 6^(th) order, the7^(th) order, the 8^(th) order, the 9^(th) order, the 10^(th) order, the11^(th) order, the 13^(th) order, the 17^(th) order, the 19^(th) order,the 23^(rd) order, the 25^(th) order and the 38^(th) order.
 4. Themethod of harmonic diagnosis for electric equipment according to claim1, wherein the degrees of deterioration are distinguished into “normal”,“caution is needed” and “defective”.
 5. The method of harmonic diagnosisfor electric equipment according to claim 4, wherein the “caution isneeded” is distinguished into light deterioration, intermediatedeterioration, and heavy deterioration according to the degrees ofdeterioration of the device.
 6. A method of harmonic diagnosis forelectric equipment to determine an abnormality of an electric motor orinverter from a current harmonic flowing to said electric motor andinverter that form electric equipment, comprising: comparing an indexvalue, which is obtained by dividing a relative harmonic content of eachorder of current harmonics by total harmonic distortion of the currentharmonics up to a predetermined order, with a criteria value, which isobtained by multiplying a harmonic function of each order found throughcalculation from the relative harmonic content of each order, whereinthe degrees of deterioration of said electric motor and inverter aredistinguished from each other by weighting said criteria value, and adeteriorated part is determined from a specific harmonic order of saidcurrent harmonics, outputting to a user.